Two scary Antarctic glaciers might be joining forces to speed up melt.

The most important part of the most important ice sheet in the world just got a bit more important this week.

Warm ocean water is already reaching much farther inland to the Pine Island and Thwaites glaciers than expected, according to a new analysis. In particular, a deep ice channel that connects the newfound warm water beneath Pine Island glacier to the much larger Thwaites may be in the process of being compromised.

“If this tributary were to retreat and get melted by warm ocean water, it could cause the melt beneath Pine Island to spread to Thwaites,” said lead author Dustin Schroeder, an assistant professor of geophysics at Stanford University.

Thwaites glacier is key to holding back disastrous sea-level rise.As I wrote back in November, Thwaites’ collapse is already inevitable — and it alone holds back enough sea-level rise to drown all coastal cities. The main question, now, is how quickly will this happen? With more bad luck, like this week’s study, as well as rising greenhouse gas emissions — the inevitable just got a little more urgent.